Catheters are used for myriad medical procedures and applications, such as in the treatment of a wide variety of vascular disorders. Catheters generally comprise an elongated shaft having at least one lumen therethrough and are inserted into a patient's body percutaneously or via natural orifices. Typically, a cardiovascular catheter is inserted percutaneously, and then advanced through the patient's vasculature to a site targeted for treatment.
A vascular catheter is typically flexible, yet sufficiently stiff so as to resist kinking while being pushed through the patient's vasculature, over a guidewire, or through a lumen of another catheter. A curved interventional guiding catheter or angiography catheter has preformed bends to locate and direct the tip of the catheter in a vessel during advancement of a treatment device, or injection of x-ray contrast media through the catheter. However, the preformed bends need to be sufficiently elastic to allow the curved portion of the catheter to be temporarily, substantially straightened while the catheter is passed through the patient's vessels until it reaches the intended position.
Typically, curved vascular catheters are initially assembled in a straight configuration and include one or more thermoplastic components. The straight catheter is deformed into a desired curve shape using tools such as an external mold or, more commonly, by inserting a stiff forming mandrel into the lumen of the catheter. To form or set the catheter in the shape of the mold or mandrel, the assembly is heated above the glass transition temperature Tg of one or more thermoplastic component(s). However, the catheter distal region that is to be curved may further comprise components that resist thermoforming at the curve-setting temperature used. These “unformable” components may be non-thermoplastic elements such as a metallic braid reinforcement layer or a tubular liner of non melt-extrudable fluoropolymer, such as polytetrafluoroethylene (PTFE). Another “unformable” component may be a thermoplastic element, such as a low-friction tubular liner having a glass transition temperature Tg above the curve setting temperature used to shape the catheter. Such “unformable” components tend to retain the original straight configuration of the catheter, thus resisting the curve shape that is heat set into the “formable” thermoplastic component(s).
Improvements in design and materials have allowed curved catheters to be constructed with increasingly thinner walls, which offer advantages such as reduced overall catheter diameter and/or increased lumen size. However, such thin walls also incur correspondingly reduced amounts of the “formable” thermoplastic components that are relied upon to overcome the inherent straightness of the “unformable” components to effectively retain the catheter's desired curve shape. Therefore, during use, the pre-curved distal region of the catheter too often tends to unbend and/or back out from the entrance of a vessel in which it was positioned. Thus, a need exists for a curved catheter having localized reinforcement of the pre-curved shape. Such reinforcement should provide the curve shape with greater stiffness while still permitting elastic straightening of the curve shape during placement. Other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims taken in conjunction with the accompanying drawings.